Goober, our resident Aldabra tortoise, weighs on average around 450 pounds and is approximately 70-years-old. His age is only an estimate, because when he arrived at the Zoo in 1968, he was already an adult. Giant tortoises are the longest-lived land animals, which means he might have another century in him! Currently, the oldest living land animal is a Seychelles giant tortoise named Jonathan who is 190 years old.
But why do tortoises live so long? As a rough rule of thumb, animals with a slower heart rate live longer than animals with a higher heart rate. This is one reason why the pygmy shrew, with the fastest heart rate of any animal at 1,200 beats per minute, lives for only a few months. By comparison, human heart rates range between 60 to 100 beats per minute. Giant tortoises clock in with a heart rate of about 10! There are several other factors also working in their favor for longevity, including genetic traits related to DNA repair, immune response and cancer suppression.
Unlike many animals in a zoo setting, Goober’s keepers can share space (the term for when a person goes into an exhibit with an animal) with him, and even more unusual for exotic animals, Goober loves being touched. He will zone out for a good neck rub, raise up like he’s on hydraulics for an armpit scratch and even enjoys a good pet on his shell. Surprisingly, turtles and tortoises are quite sensitive through their shells.
A tortoise shell has a base of fused rib bone and spine called the carapace. This carapace is covered by smaller plates called scutes which are made of keratin—the same stuff in fingernails and rhino horns. The underside portion of a tortoise is covered by the plastron, which is constructed similarly as the carapace, with bony plates covered by scutes. The carapace and plastron are connected on the sides by a bridge, and together they form the tortoise shell.
With his tough exterior and no natural predators, Goober is a deep sleeper. On your next visit, you’re most likely to see him zonked out with his head lying flat on the ground or enjoying his diet of leafy greens, vegetables, tortoise chow and the occasional banana as a treat. And hopefully you’ll see him for another 100 years!